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CVE.org (no NVD analysis yet)· CNA Linux

CVE-2026-99254: io_uring: don't flood a cancelling task with task_work

Noroxi assessment

Priority: Monitor (action score 0/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
  • Fixed version: Linux Linux 14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9, 22e643e61b9b6299b42ff7d88bab48bccada8a5d, 2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9, 22e643e61b9b6299b42ff7d88bab48bccada8a5d, 2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: io_uring: don't flood a cancelling task with task_work io_ring_exit_work() asks each task which has used the ring to remove its tctx node, by task_work, and repeats that until the list is empty. io_tctx_exit_cb() doesn't touch the node while the task is in io_uring_cancel_generic(), which removes all the nodes at its end. So the work item queues the callback again as soon as it has completed, for nothing. That is more than a waste of time. task_work_run() only returns when it finds the list empty. If the rings are released from inside the cancellation, because requests of other rings held the last references to their files, up to 64 work items keep sending callbacks to the one task which is running them. It never finds the list empty, never gets back to the cancellation, the nodes stay, and so it goes on: a task with 60 pairs of rings which poll each other ran 280000 callbacks in 5 seconds, 20 seconds after exit_group(). It ends when all the senders happen to be late at the same time. Until then the task keeps a CPU and the work items busy. An exiting task can't be killed meanwhile. execve() cancels the requests in the same way, so a live task can get stuck there as well, for minutes. If it takes more than five, the work items run into the WARN_ON_ONCE(time_after(jiffies, timeout)) of io_ring_exit_work(). No privilege is needed for any of this. If the callback has met a task in cancellation, wait a little before it is sent again. Nobody has to wake the work item up for that: either the node is gone by then, or it is the turn of the next round.

—No exploit Fix available
Published
Nov 3, 2026
Updated
Nov 3, 2026
EPSS
0.1% · 9th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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  • Not in KEV: no record of exploitation in the wild
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  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.12affected
    • d56d938b4bef3e1421a42023cdcd6e13c1f50831 and later · before a22fb44e988b01b82235ea07f0bf0fc73e256596affected · git
    • d56d938b4bef3e1421a42023cdcd6e13c1f50831 and later · before 2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1affected · git
    • d56d938b4bef3e1421a42023cdcd6e13c1f50831 and later · before 61c761fc21e00e45c33c2bb596be442d92fb8792affected · git
    • d56d938b4bef3e1421a42023cdcd6e13c1f50831 and later · before 14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9affected · git
    • d56d938b4bef3e1421a42023cdcd6e13c1f50831 and later · before abdc57c7ebabaaf0b622178a6a85834e1e54ff80affected · git
    • d56d938b4bef3e1421a42023cdcd6e13c1f50831 and later · before 22e643e61b9b6299b42ff7d88bab48bccada8a5daffected · git
    • before 5.12not affected · semver
    • 6.1.191 and later · up to and including 6.1.*not affected · semver
    • 6.6.161 and later · up to and including 6.6.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.115-16.12.115-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-99251Nov 3, 2026 · Drivers: hv: Avoid infinite retry loop in init_vp_index()
    0Monitor
  • ← EarlierCVE-2026-99253Nov 3, 2026 · io_uring/cancel: rearm local work wake up before sleep
    0Monitor
  • Later →CVE-2026-99255Nov 3, 2026 · io_uring/io-wq: don't hide a link from cancellations
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux14f56e9c0b8fdc2e178acdbec9781e90ef46f7e9Vendor (CNA)
Linux Linux22e643e61b9b6299b42ff7d88bab48bccada8a5dVendor (CNA)
Linux Linux2c75ebae8a7f09c99e31c7042b7d4d595f03b2b1Vendor (CNA)
Linux Linux61c761fc21e00e45c33c2bb596be442d92fb8792Vendor (CNA)
Linux Linuxa22fb44e988b01b82235ea07f0bf0fc73e256596Vendor (CNA)
Linux Linuxabdc57c7ebabaaf0b622178a6a85834e1e54ff80Vendor (CNA)
debian:linux6.12.115-1 · Debian:13Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 5, 2026+2 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Exploit maturity— → none
  2. Fix✗ → ✓

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References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records